What you can do

Please submit a patch that improves the error message. A good better error
message would be:

# for non-recursive structures:
Sorry, structures on both sides of non-dwimmy hyperop are not of same shape
left: 3 elements
right: 2 elements
# for recursive structures:
Sorry, structures on both sides of non-dwimmy hyperop are not of same shape
left: 3 elements
right: 2 elements
at nesting level 2